Unique

1. (not comparable) Being the only one of its kind; unequaled, unparalleled or unmatched. Synonyms: one of a kind, sui generis, Singular, one-off
2. Of a feature, such that only one holder has it.
3. Particular, characteristic.
4. (often proscribed) Rare or unusual.

Usage notes

• The comparative and superlative forms uniquer or more unique and uniquest or most unique, as well as the use of unique with modifiers as in fairly unique and very unique, are criticised with the reasoning that either something is unique or it is not. These modified senses of “unique”, however, have been in use since at least as far back as the 18th century, with “unique” taking its common secondary sense of “uncommon, unusual, remarkable”.